This invention relates to a method of and means for making a metallic bond to powdered metal parts and more particularly to a method of and means for brazing to powdered metal parts through the use of a beam of coherent electromagnetic energy.
In recent years, it has been found advantageous to make metal parts for use in a wide variety of applications by compacting metal powders through the use of heat and pressure into solid bodies of the desired shape and size. Such parts made of compacted powdered metal can be designed to provide unusual physical characteristics, not obtainable with conventional alloying techniques, by selection of the metal powder or mixture of metal powders which are compacted to form the desired solid body.
However, powdered metal parts have the disadvantage that is has been difficult, if not impossible to make a metallic bond to such parts. Attempts to weld powdered metal parts to other metal parts have failed because of the heat required to raise a joint therebetween to the melting temperature of both parts in order to produce a satisfactory weld. Thus, the powdered metal parts may actually crumble or fall apart during or after the welding process because of internal stresses resulting from excessive heating.
Attempts to braze powdered metal parts to other parts have been only slightly less unsatisfactory due to the excessive absorption of the molten braze material into the powdered metal parts. In conventional processes of heating the braze material to its melting temperature, the powdered metal part is also heated. Although the temperatures involved in brazing are lower than the temperatures required for welding and weakening of the powdered metal parts thereby is correspondingly less, it has been found that such heating of the powdered metal parts will cause excessive amounts of the braze material to be drawn into or absorbed by the powdered metal parts by a capillary action which is a function of the temperature reached by the parts.
Thus, if sufficient heat is used to provide a satisfactory braze, an excessive amount of inherently expensive braze material will be required and it will be difficult to insure an even distribution of the braze material throughout the braze joint. In addition, the absorption of the braze material into the powdered metal parts will tend to change the desired physical characteristics of powdered metal parts at least in the vicinity of the braze joint and usually throughout a sufficient volume to defeat the purpose of using the powdered metal part.
It is a principal object of this invention to provide a method of and means for making metallic bonds to powdered metal parts without excessive change in the desired physical characteristics of the powdered metal parts or the use of excessive amounts of expensive materials.